html, body {
  width: 100%;
  height: 100%;
}

body {
  background: url();
}

#sketch {
  border: 10px solid gray;
  height: 100%;
  position: relative;
}

#tmp_canvas {
  position: absolute;
  left: 0px; right: 0;
  bottom: 0; top: 0;
  cursor: crosshair;
}

form {
  padding: 10px; margin: 10px;
  background: whiteSmoke;
}